The invention relates to improvements in apparatus for converting tubular blanks of ductile material into spacer frames for use in multiple-pane windows. More particularly, the invention relates to improvements in apparatus for making spacer frames which are or which can be filled with a flowable hygroscopic material (desiccant) serving to absorb moisture which happens to penetrate into the space between the panes of a multiple-pane window so that the moisture cannot cloud the panes to thus affect the light-transmissivity and appearance of the window.
Commonly owned U.S. Pat. Nos. 4,627,263 and 4,720,950 disclose an apparatus wherein intermediate portion of a hollow tubular blank is converted into an elbow (i.e., into a substantially L-shaped or V-shaped body) by bending the intermediate portion around an anvil with assistance from a device which bends the tubular body about the anvil and by resorting to a roller which engages the intermediate portion of the blank opposite the anvil. Such apparatus are quite suitable for the making of satisfactory spacer frames from thick-walled blanks. The roller serves to stretch the material of the adjacent portion of the blank, and the roller can be oscillated at a desired frequency to promote the flow of the material of the blank in the region where the blank is being caused to overlie the anvil.
Problems arise when the walls of the tubular body are thin or very thin. Such tubular bodies are preferred in many instances in order to reduce the cost of spacer frames and of entire windows wherein spacer frames are used to maintain the panes at a given distance from each other as well as to confine a supply of desiccant which absorbs moisture (if any) from the space between the panes. When the walls of the tubular body are very thin, they cannot stand a pronounced rolling operation, i.e., a reduction of wall thickness in addition to that which necessarily takes place as a result of bending an intermediate portion of a tubular blank about an anvil. Attempts to convert thin-walled blanks in accordance with heretofore known procedures have met with failure, primarily because the deforming operation is unpredictable (i.e., the walls develop cracks and/or creases) and also because the number of rejects is excessive. In addition, if the tubular blanks are made of a higher-quality material, such as iron or steel, the material offers a pronounced (and often excessive) resistance to treatment by a roller or the like.